Lathe wih two-opposed spindles

ABSTRACT

There is provided a multi-turret lathe with two opposed spindles which is capable of machining a workpiece more effectively. The lathe with two opposed spindles includes: a first spindle ( 2 ); a second spindle ( 4 ) located opposite to the first spindle on the same axis and movable toward and away from the first spindle; and a set of two tool turrets ( 8   a  and  8   c ) which machines a workpiece cooperating with the first spindle, and another set of two tool turrets ( 8   b  and  8   d ) which machines a workpiece cooperating with the second spindle, and the two tool turrets in each of the sets are disposed opposite to each other about a spindle axis (B). Each of the four tool turrets is mounted on a tool slide which is movable and positionable in the direction of spindle axis and also in the direction perpendicular to the spindle axis. This enables each of the four tool turrets to be movable from a position to machine a workpiece held on one of the spindles and another position to machine a workpiece held on the other spindle.

TECHNICAL FIELD

[0001] The present invention relates to a multi-turret lathe with twoopposed spindles comprising two spindles coaxially opposed to each otherand a plurality of tool turrets co-operable with the spindles formachining a workpiece.

BACKGROUND ART

[0002] The lathe with two opposed spindles comprising two spindlescoaxially opposing to each other is known in the art. The conventionallathes hold one end of a workpiece to machine the workpiece and that endcannot be machined while it is being held. In the lathe with two opposedspindles, however, the partially machined workpiece can be transferredfrom one spindle to the other, and each of the ends of the workpiecewhich has been held by a chuck of either one of the spindles can bemachined on the same machine.

[0003] If the lathe with two opposed spindles includes a plurality oftool turrets, two different machining operations can simultaneously beperformed for two workpieces held by two different spindles. Thisimproves the efficiency of working. The tool turrets may be providedwith rotary tools such as drills and milling cutters, tailstocks,supporting rollers which support the workpiece at the periphery thereof,and the like. When these tools are mounted on the tool turrets in anappropriate combination, the workpiece can be subjected to a broad typeof machining operations.

[0004] A lathe with two opposed spindles in a prior art is classifiedinto two-spindle and two-turret type and two-spindle and three-turrettype. The two-spindle and two-turret type lathe comprises two spindlesand two turrets each cooperating with the corresponding spindle formachining a workpiece. In such an arrangement, a single workpiece heldby one of the spindles can be machined by use of two tool turrets. Forexample, when the workpiece is held at one side by a chuck of one of thespindles, the opposite side of the workpiece may be held by a tailstockwhich is mounted on a tool turret cooperating with the other spindle forlathe-turning. However, this disables the machining of a workpiece onthe other spindle.

[0005] In the two-spindle and three-turret type lathe, usually, thethird turret is movable from a position in which a workpiece supportedby the first spindle is to be machined to another position in which aworkpiece supported by the second spindle is to be machined. Each of thefirst and second spindles can cooperate with two turrets to machine theworkpiece as necessary. For example, a workpiece held by one spindle canbe lathe-turned or drilled while simultaneously machining the externaland internal diameters of the workpiece by use of two turrets on theother spindle.

[0006] If a workpiece held by one spindle is machined by use of two toolturrets, a reaction force on the workpiece being machined can bebalanced by cutting the workpiece at two positions opposite to eachother about the axis of the spindle. This enables various types ofmachining operations such as machining a shaft by use of a tailstockmounted on one turret, simultaneous cutting of external and internaldiameters and so on which could not be performed by the conventionalone-turret lathes with one spindle. Furthermore, the efficiency ofworking can be improved since the workpiece can be machinedsimultaneously at two positions.

[0007] However, the three-turret lathes with two spindles used in theprior art can only use one turret for one spindle when the third turretis used cooperating with the other spindle. Thus, machining using twoturrets cannot be performed on the one spindle until the working withthe third turret has been completed.

DISCLOSURE OF THE INVENTION

[0008] The present invention provides a multi-turret lathe with twoopposed spindles which can more effectively machine a workpiece. Thepresent invention can economically realize broad types of machining byproviding a reasonable structure in which a tool can be moved andpositioned in a direction (Y-axis) orthogonal to the direction ofspindle (Z-axis) and the direction of tool cutting (X-axis).

[0009] A lathe with two opposed spindles of the present inventioncomprises: a first spindle 2; a second spindle 4 located opposite to thefirst spindle on a spindle axis of the first spindle and movable andpositionable in a direction of the spindle axis; and a set of two toolturrets 8 a and 8 c which machines a workpiece cooperating with thefirst spindle, and another set of two tool turrets 8 b and 8 d whichmachines a workpiece cooperating with the second spindle. The two toolturrets in each of the sets are disposed opposite to each other at aforward-downward side and a backward-upward side of the spindle axis B,respectively.

[0010] It may be most preferred that each of the four tool turrets intwo sets is mounted on a tool slide which is movable and positionable inthe directions of Z-axis and X-axis. It may be further preferred thateach of the four tool turrets is independently movable from a positionto machine a workpiece held by the first spindle to another position tomachine a workpiece held by the second spindle. At least one of twoopposing tool turrets in one set may include a device for driving rotarytools such as a drill and a milling cutter.

[0011] In a more preferred lathe with two opposed spindles of thepresent invention, may include a second spindle 4 and a first spindleimmovable in a direction of spindle axis, the second spindle 4 and thefirst spindle may be arranged next to each other as viewed from anoperator on the machine base. One of the two tool turrets cooperatingwith each of the spindles may be disposed at a backward-upward side ofthe spindle axis B while the other of the two tool turrets be disposedat a forward-downward side of the spindle axis. All of the four toolturrets may be movable and positionable in a direction of spindle axisand in a direction perpendicular to the spindle axis.

[0012] In a further preferred lathe with two opposed spindles of thepresent invention, may comprise a device for moving and positioning toolturrets disposed on a backward-upward side of the spindle axis (B), in adirection of Y-axis, and the backward tool turret may include a devicefor driving a rotary tool. In such a structure, the tool turret disposedon a forward-downward side of the spindle axis B may include no Y-axismoving and positioning device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic view of a lathe with two opposed spindlesaccording to one embodiment of the present invention, as viewed fromarrow C in FIG. 2.

[0014]FIG. 2 is a side view of the lathe shown in FIG. 1.

[0015]FIG. 3 is a perspective view of a tool slide in the lathe of FIG.1.

[0016] FIGS. 4 to 7 schematic views illustrating working operations ofthe lathe according to the aforementioned embodiment as viewed from thearrow C in FIG. 2.

[0017] In the drawings: reference numeral 2 denotes a first spindle; 4 asecond spindle; 7 a bed; 8 a to 8 d tool turrets; 9 spindle guides; 11 aand 11 c Z-axis guides; 12 a to 12 d X-axis guides; 14 Y-axis guides; Aa working region; and B a spindle axis.

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Referring now to FIGS. 1 and 3, a first headstock 1 is stationaryin a direction of spindle axis (or Z-axis). The first headstock 1supports a first spindle 2 for high-speed rotation, low-speedhigh-torque rotation and indexing movement. A second spindle 4 isdisposed opposed to the first spindle 2 on the same spindle axis B andis supported by a second headstock 3. The second headstock 3 can bemoved toward and away from and positioned relative to the first spindle2 along spindle guides 9 on a bed 7. The second spindle 4 can behigh-speed rotated, low-speed and high-torque rotated and indexed by adrive motor (not shown), as in the first spindle 2. The opposing ends ofthe first and second spindles 2, 4 include first and second chucks 5, 6mounted thereon, respectively.

[0019] The first and second spindles 2 and 4 are positioned laterallyrelative to each other about a working area A, as viewed from anoperator. As been clearly shown in FIG. 2, the bed 7 is of so-calledslant type in which a bed 7 is sloped lower toward the side of operator.Forward and backward Z-axis guides 11 a and 11 c are disposed parallelto the spindle axis B on the forward and backward sides of the spindleaxis of the bed, respectively. Since the bed 7 is of slant type, theforward Z-axis guide 11 a is positioned on the forward-downward side ofthe spindle axis B while the backward Z-axis guide 11 c is positioned onthe backward-upward side of the spindle axis B, as viewed from theoperator.

[0020] Slides 25 a and 25 b are slidably mounted on the Z-axis guide 11a on the sides of the first and second spindles, respectively, whileslides 25 c and 25 d are slidably mounted on the Z-axis guide 11 c onthe sides of the first and second spindles, respectively. Z-axis feedscrews 26 a and 26 b are operably supported by the bed parallel to theZ-axis guide 11 a while Z-axis feed screws 26 c and 26 d are operablysupported by the bed parallel to the Z-axis guide 11 c. Each of theZ-axis feed screws is operably connected to the corresponding one ofZ-axis feed motors 27 a, 27 b, 27 c and 27 d. Each of the Z-axis feedscrews 26 a, 26 b, 26 c and 26 d is threadingly screwed into thecorresponding one of the slides 25 a, 25 b, 25 c and 25 d.

[0021] The slides respectively include an X-axis guide 12 a, 12 b, 12 cand 12 d; an X-axis feed screw 36 a, 36 b, 36 c and 36 d parallel to thecorresponding X-axis guide and an X-axis feed motor 37 a, 37 b, 37 c and37 d connected to the end of the corresponding X-axis feed screw. Eachof tool slides 13 a and 13 b is movably mounted on the corresponding oneof the X-axis guides 12 a and 12 b in the forward slide, and threadinglyscrewed over the corresponding one of the X-axis feed screws 36 a and 36b. Each of X-axis slides 35 c and 35 d is movably mounted on thecorresponding one of the X-axis guides 12 c and 12 d in the backwardslide, and threadingly screwed over the corresponding one of the X-axisfeed screws 36 c and 36 d.

[0022] Each of the X-axis slides 35 c and 35 d is of L-shaped sidecross-section and comprises a Y-axis guide 14 c or 14 d, a Y-axis feedscrew 46 c or 46 d extending parallel to the corresponding one of theY-axis guides and a Y-axis feed motor 47 c or 47 d connected to thecorresponding one of the Y-axis feed screws. Each of tool slides 13 cand 13 d is movably mounted on the corresponding one of the Y-axisguides 14 c and 14 d in each X-axis slide and threadingly screwed overthe corresponding one of the Y-axis feed screws 46 c and 46 d.

[0023] The four tool slides thus respectively mounted include a toolturret 8 a, 8 b, 8 c and 8 d mounted thereon. The tool turrets 8 a and 8b positioned forward are located below the spindle axis B and movableand positionable in the directions of Z- and X-axes. The tool turrets 8c and 8 d positioned backward are located above the spindle axis B andmovable and positionable in the directions of Z-, X- and Y-axes.

[0024] The slides 25 a, 25 b, 25 c and 25 d are dimensioned and arrangedsuch that the slides 25 a and 25 c on the side of the first spindle areretractable from the working region A when the tool turrets 8 b and 8 don the side of the second spindle are moved towards the first spindlefor machining a workpiece 15 a held by the first spindle, and such thatthe slides 25 b and 25 d on the side of the second spindle areretractable from the working region A when the tool turrets 8 a and 8 con the side of the first spindle are moved towards the second spindlefor machining a workpiece 15 b held by the second spindle.

[0025] The basic workpiece machining operation in the lathe with twoopposed spindles thus configured is described below. A workpiece iscarried to the working region A by a loader (not shown) or inserted intothe working region A through a hollow bore of the first spindle, andthen held by the first chuck 5. The workpiece is machined by cuttingtools or tailstocks attached to the two tool turrets 8 a and 8 c on theside of the first spindle.

[0026] After the machining operation on the side of the first spindlehas completed, the second spindle 4 is then moved to the side of thefirst spindle. The workpiece is held by the second chuck 6 at themachined end thereof. Next, the first chuck 5 is opened or the first andsecond spindles are synchronously rotated to separate the machinedworkpiece by use of a cutting-off tool. Thereafter, the second headstock3 is moved away from the first headstock 1. Thus, the workpiece istransferred to the side of the second spindle. The workpiece is thenmachined by cutting tools or tailstocks mounted on the tool turrets 8 band 8 d on the side of the second spindle.

[0027] After the workpiece has been transferred to the second spindle,another workpiece is loaded on the first spindle. The workpieces aremachined on the sides of the first and second spindles by use of twopairs of tool-turrets, respectively.

[0028] FIGS. 4 to 7 schematically illustrate the machining operations bythe lathe of the present invention. In FIG. 4, the workpiece 15 a, whichis loaded on the first spindle, is machined in a balanced fashion byexternal-diameter machining tools 16 a and 16 c respectively mounted onthe tool turrets 8 a and 8 c on the side of the first spindle. Theexternal and internal diameters of the workpiece 15 b, which is loadedon the second spindle, is simultaneously machined by anexternal-diameter machining tool 16 d and an internal-diameter machiningtool 17 which are respectively mounted on the tool turrets 8 b and 8 don the side of the second spindle. The balanced machining operation canavoid lowering the machining accuracy or generating vibration by movingthe tools to the workpiece from two directions opposite to each otherabout the spindle axis B to machine the workpiece so that the machiningreactions acting on the workpiece is balanced to prevent deformation inthe workpiece due to the heavy cutting.

[0029] In FIG. 5, the end of the workpiece opposite to the chuck, whichis loaded on the first spindle, is machined by a tool 16 c mounted onone of the turrets 8 c while being held by a tailstock 21 mounted on theother turret 8 a on the side of the first spindle. On the other hand,the workpiece 15 b, which is loaded on the second spindle, is machinedby a tool 16 d mounted on the other tool turret 8 d while the peripheryof the workpiece being supported by a support roller 22 which is mountedon the tool turret 8 b on the side of the second spindle.

[0030] In FIG. 6, the workpiece 15 a loaded on the first spindle ismachined by the tool 16 b mounted on one of the tool turrets 8 b on theside of the second spindle while the workpiece 15 b loaded on the secondspindle is machined by the tool 16 c mounted on one of the tool turrets8 c on the side of the first spindle. At this time, the other toolturrets 8 a and 8 b on the sides of the first and second spindles arebeing retracted at the end portions of the Z-axis guides 11 a and 11 c.Such a machining operation generally lowers the efficiency of machining,but is effective in the case where many types of tools are required tomachine the workpiece.

[0031] In FIG. 7, an elongated workpiece 15 is held at one end by thefirst spindle and the other end by the second spindle, and machined inthe balanced fashion by the external-diameter machining tools 16 b and16 d respectively mounted on the tool turrets 8 b and 8 d on the side ofthe second spindle. The tool turrets 8 a and 8 c on the side of thefirst spindle are being retracted at the ends of the Z-axis guides 11 aand 11 c. Such a machining operation is effective in the case ofsmoothly machining the elongated workpiece from one end to other withoutleaving any cutting trace.

INDUSTRIAL APPLICABILITY

[0032] If a workpiece is machined by a tool mounted on one of the toolturrets while supporting that workpiece by a workpiece supporting membersuch as a tailstock or support roller mounted on the other tool turreton the side of first and second spindle in the lathe with two opposedspindles as shown in FIG. 4, an elongated shaft material having a largerlength compared to a diameter thereof can be machined simultaneously onthe sides of the first and second spindles. This can improve theefficiency of machining the shaft material.

[0033] If two tool turrets cooperating with the first and secondspindles, respectively, are simultaneously used as shown in FIG. 5, theefficiency of machining can be improved. When the balanced machiningoperation is performed for heavy cutting, the efficiency of machiningcan further be improved.

[0034] When a workpiece held on one of the spindles is machined by atool mounted on a tool turret of the other spindle as shown in FIG. 6,machining requiring various types of tools can be implemented. When theentire length of a workpiece is machined by a tool mounted on a toolturret on the side of the first or second spindle as shown in FIG. 7,the finishing accuracy for surface can further be improved.

[0035] In such a structure that the first headstock 1 is stationary asin the lathe of the illustrated embodiment, the rigidity on the side ofthe first spindle can be increased. This enables the reasonablemachining operation matching the order of workpiece delivery in which aworkpiece is finished on the side of the second spindle after it hasbeen roughly machined on the side of the first spindle. The structure inwhich all the four tool turrets are independently movable andpositionable in the direction of spindle axis and also in the directionperpendicular to the spindle axis through CNC device is superior inrespect of the freedom of machining, the improvement of machiningefficiency and the easy control.

[0036] In such a structure that the backward tool turrets are movable inthe direction of Y-axis as in the lathe of the illustrated embodiment,they may include rotary tools such as drills and milling cutters mountedthereon to perform a complicated machining operation near the machiningcenter. When only the backward tool turrets are movable in the directionof Y-axis, various broad types of machining operations can be performedby Y-axis movable tools. This can also avoid increasing themanufacturing cost for the machine. Since the Y-axis moving devicehaving its increased height is located backward in the machine, theoperability by an operator in the working region can be ensured.

1. A lathe with two opposed spindles comprising: a first spindle (2); a second spindle (4) located opposite to the first spindle on the same axis and movable toward and away from the first spindle; and a set of two tool turrets (8 a and 8 c) which machines a workpiece cooperating with the first spindle, and another set of two tool turrets (8 b and 8 d) which machines a workpiece cooperating with the second spindle, wherein the two tool turrets in each of the sets are disposed opposite to each other about a spindle axis (B), wherein each of the tool turrets is mounted on a tool slide which is movable and positionable in a direction of spindle axis and in a direction perpendicular to the spindle axis, except one of the tool turrets that cooperates with the spindle (4) which is movable toward and away from the first spindle in a direction of spindle axis, and wherein the one tool turret is movable and positionable at least in a direction perpendicular to the spindle axis.
 2. A lathe with two opposed spindles comprising: a first spindle which is mounted in a stationary position (2); a second spindle (4) located opposite to the first spindle on the same axis and movable toward and away from the first spindle; and a set of two tool turrets (8 a and 8 c) which machines a workpiece cooperating with the first spindle, and another set of two tool turrets (8 b and 8 d) which machines a workpiece cooperating with the second spindle, wherein the two tool turrets in each of the sets are respectively disposed at a forward-downward side and a backward-upward side of the spindle axis (B) as viewed from an operator, and wherein all of the four tool turrets are movable and positionable in a direction of spindle axis and in a direction perpendicular to the spindle axis.
 3. The lathe with two opposed spindles as defined in claim 2 or 3, wherein all of the four tool turrets are independently movable from a position to machine a workpiece held on the first spindle to another position to machine a workpiece held on the second spindle.
 4. The lathe with two opposed spindles as defined in claim 2 or 3, wherein each of the tool turrets (8 c and 8 d) disposed at a backward-upward side of the spindle axis (B) includes a rotary tool driving device.
 5. The lathe with two opposed spindles as defined in claim 2 or 3, wherein two tool turrets disposed on a backward-upward side of the spindle axis (B) are movable and positionable in a direction of Y-axis.
 6. The lathe with two opposed spindles as defined in claim 2 or 3, wherein each of the two tool turrets (8 c and 8 d) disposed at a backward-upward side of the spindle axis (B) includes a rotary tool driving device and is movable and positionable in a direction of Y-axis. 